Thread chain trimming device for sewing machines



April 23, 1968 H. TIEMANN 3,379,151

THREAD CHAIN TRIMMING DEVICE FOR SEWING MACHINES Filed Jan. 17, 1967 3 Sheets-Sheet l INVENTOR b f/fZ/VUT T/F/M/V/I/ JM AM A T PR VE) H. TIEMANN April 23, 1968 THREAD CHAIN TRIMMING DEVICE FOR SEWING MACHINES 3 Sheets-Sheet 2 Filed Jan. 17, 1967 FIG] INVENTOR 4 #51 M07 T/F/VA/V/V 2% Adam,

19 Tran E/ April 23, 1968 H. TIEMANN 3,379,151

THREAD CHAIN TRIMMING DEVICE FOR SEWING MACHINES I '5 Sheets-Sh l, 5 Filed Jan. 17, 1967 69 H6! M07 T/EMA N MQAW Ar TOR/VE/ United States Patent 0 ABSTRACT OF THE DISCLOSURE A device for trimming the thread chain formed between successive pieces of work fed through a sewing machine during its operation, at the beginning and end of the seam. A movable knife is mounted beyond the path of motion of the work piece, is moved with the feed dog, and co-acts with a fixed counter knife. A mechanism for the automatic insertion of the thread chain between the knives is provided.

Background of the invention The object of the invention is to provide means for the independent trimming of the thread chain formed between successive pieces of work fed through a sewing machine, especially an overedge sewing machine, during its operation at the beginning and the end of the seam, without dismembering the thread chain section cuttings and without the application of auxiliary means, such as vacuum or compressed air, while employing comparatively Simple mechanical means.

There are already known such devices for trimming the thread chains, in which the thread chain to be severed is guided between two permanent shearing knives by means of vacuum or compressed air. These are described in US. Patent 3,143,987 to H. F. Daniel et a1., entitled Thread Chain Severing Device for Sewing Machines, US. Patent 3,149,594, to A. I. Buckreus et al., entitled Method and Apparatus for Trimming Stitches.

When using compressed air or vacuum for guiding the thread chain into the trimming device, it is necessary to attach to the sewing machine an additional vacuum or compressed air pump if the sewing machine is to remain free from further connections to possibly existing central compressed air or vacuum plants. Since the necessary quantity of air and its pressure is relatively great, the use of this medium for the present purpose is not regarded as profitable, in view of the high cost of production of compressed air. However, there are known automatic mechanical devices for trimming the threads, in which the cutting knives are permanently connected with the driving device through a number of connecting links such as rotating shafts, guide rods disclosed in German Patent 241,357, of Dec. 25, 1910. The sewing speed is considerably limited by these additionally moving machine parts.

This is also true of arrangements which have a clutch mounted between the movable knife and a driving part of the sewing machine, one clutch half of which is carried by a machine part supported on the web of fabric. After discharging the web of fabric, the machine part is lowered and thereby the clutch part is brought into the path of the permanently driven clutch part. Such an arrangement is disclosed in German Patent 559,593, of Feb. 7, 1928.

However the operation of this device is unreliable, since the presser for interlining the device, must reach a certain low position above the throat plate.

The position in the vertical sense in which the cutting device may be interposed is lower than the thickness of Patented Apr. 23, 1968 the work piece. This device is therefore not adapted for thin fabrics, since the path of operation necessary for coupling the cutting device is too short. A further disadvantage is that the cutting device is in constant operation after its Coupling, so that the thread chain formed between successive pieces of work is cut into a plurality of small parts. Thereby the development of clogging and dust in the machine is unavoidable.

Finally, there have additionally become known thread chain trimming devices in which the trimming of threads is effected by grinding, as disclosed in German Patent 751,969, of Dec. 28, 1940, or in which the severing is effected by means of two cooperating thread cutting members, which are formed at the presser foot and the feed dog behind the needle and which are held apart by the passing work piece. However, these simple mechanisms are disadvantageous, in that their trimming members are in permanent engagement with each other and therefore are subjected to extensive abrasion. Moreover, the thread chain formed between successive pieces of work is likewise cut into a plurality of small parts.

Summary According to the invention, the above problems are solved substantially by the provision of a deflecting channel for the thread chain arranged behind the needle and a thread chain feeding dog for the transportation of the deflected thread chain sideways of and parallel to the cutting knives in the feed di ection of the workpieces, whereby the movable knife is carried by the feed dog for the work piece.

The deflection channel, which is situated in the throat plate, exhibits a deflecting edge for the thread chain. The deflecting edge extends angularly to the path of motion of the work piece and away from this path.

A leading groove, likewise extending angularly to the path of motion of the work piece and away from this path, is provided in the presser foot. The thread chain feeding dog, which is connected with the feed dog for the work piece, consists of a geared feed element, positioned beyond the throat plate and cooperating with a guiding surface, and extending parallel to the trimming knives.

The guiding surface for the thread chain comprises a knife clip carrying the counter knife, whereby the knife clip is provided with a deflector for the trimmed ends of the thread chain.

A slippage ending in a waste channel, which is mounted at a right angle to the sewing machine is provided for the evacuation of the trimmed ends of the thread chain out of the machine.

Brief description of the drawings FIG. 1 is a side elevation of an overedge sewing machine in which the present invention is embodied.

FIG. 2 is an enlarged plan view of the trimming device, a work piece furnished with an overedge seam and the trimming of the thread chain at the end of the work piece.

FIG. 3 is a view similar to FIG. 2, immediately before the beginning of trimming the thread chain at the start of the work piece.

FIG. 4 is a cross-section taken on line IV1V of FIG. 2.

FIG. 5 is a perspective view of the throat plate with the deflecting channel for the thread chain and the feed dog carrying the trimming knife and the thread chain feeding dog.

FIG. 6 shows a perspective view of the feed dog for the workpiece and the thread chain feeding dog.

FIG. 7 is a perspective view of part of the machine with the thread trimming device of this invention and 3 FIG. 8 is a perspective view of the presser foot, the throat plate, the feed dog and the deflection of the thread chain.

Description of the preferred embodiment The invention comprises an overedge sewing machine shown in FIG. 1 and having a socket 1, a work supporting member 2, a presser foot 4 carried by a presser bar 3, an eyed and curved needle 5, and all usual elements for an overedge sewing machine.

As may be seen in the drawings, the throat plate 6 has a stitch tongue 7 for producing an elastic thread chain 8 in cooperation with the needle 5, which is shown in FIG. 1, and with overedge loopers (not shown). The throat plate 6 has parallel slots 9, 10 for the passage of the feed dogs 12 and 13 (FIG. 2), which are developed with feed teeth 11. Throat plate 6 is further shaped with a deflecting channel 14 for the thread chain 8, having a deflecting edge 16, which extends angularly to the path of motion of the work piece 15 and away from this path.

The feed dog 12 is fastened in known manner to a feed bar 17 by means of a screw 18. The feed dog 12 has two rows of feed teeth 11 and carries a thread chain feeding dog 19, which is likewise provided with a row of teeth 20. A movable knife 22 is fastened to the feed dog 12 by means of a screw 21, whereby the knife 22 co-acts with a counter-knife 23. This is secured by means of screws 24 to a knife clip 25, which is rigidly secured to the sewing machine. The knife clip 25 (FIGS. 4 and 7) is shaped with a thread chain guiding surface 26 for the thread chain in the area of which operates the thread chain feeding dog 19.

The knife clip 25 is provided with a vaulted deflector 27 for the cut thread chain rests 8, for the purpose of leading the chain rests 8 into a slippage 28 (FIGS. 1 and 7) out of the machine. The slippage 28 ends in a waste channel 29 which is mounted at a right angle to the sewing machine.

In the sole of the presser foot 4 (FIGS. 4 and 8) there is formed a leading groove 30 for the thread chain 8 lying in the section of the deflecting channel 14 of the stitch plate 6. The leading groove 30 likewise extends angularly of the path of motion of the work piece 15 and away from this path. The operation of the thread chain trimming device may be described as follows:

The work piece 15, supplied with overedge stitches 31 on its edges, is removed rearwardly manually by the operator after leaving the feed dog device 12, and while the machine is still running at a speed which is below the speed of the feed dog 12. Hereby and due to the continual running of the machine, the continually formed thread chain which is behind the workpiece will be deflected by the deflecting edge 16 of the deflecting channel 14 and the leading groove 30 shaped on the presser foot 4 (FIG. 8) to the thread chain feeding dog 19, fastened to the feed dog 12. Hereby the thread chain 8 gets into the knives 22, 23, the movable knife 22 of which operates in rhythm with the feed dog 12. The thread chain 8 is cut off in such a manner that only a little thread chain rest remains at the end of the work piece 15. After introduction into the machine and before entering into the stitch forming means 5, the work piece 15 will be cut off by an edge cutting knife 32.

During the feeding of the work piece 15', the thread chain 8, disposed between the guiding surface 26 and the thread chain feeding dog, is transported backwards to the slippage 28 along the deflector 27 (FIG. 7).

Due to the stiffness of the work piece 15' and its straight feeding, the thread chain 8 is not deflected to the right side of the thread chain feeding dog 19 by passing the deflecting channel 14 and the deflecting edge 16. Instead, it gets into the knives 22 and 23, whereby it is cut through, so that only a little thread chain rest 8 remains at the beginning of the work piece 15'.

Consequently, the cut thread chain 8 at the end and the beginning of workpieces 15, 15' now slides on the slope of the slippage 28 and thence falls into a Waste bin (not shown) which is arranged underneath the table.

What I claim is:

1. In a sewing machine, means adapted to form a thread chain between successive work pieces fed through the stitch forming mechanism of the sewing machine including a throat plate, a feed dog reciprocating in said throat plate for engaging and advancing a work piece thereon in a predetermined path of movement, a presser foot for holding the work piece in engagement with said throat plate and feed dog, and thread trimming means for the thread chain at the beginning and the end of the seam, comprising a thread chain feeding dog, a stationary knife and a movable knife co-acting with said stationary knife mounted beyond the moving path of the work piece, said thread trimming means having a deflection channel for said thread chain, said deflection channel arranged behind the needle, said thread chain feeding dog for the transportation of the deflected thread chain being carried by the feed dog, and said movable knife mounted on said feed dog, said deflected thread chain running sideways of and parallel to said trimming means in the feed direction of the work pieces.

2. In a sewing machine as set forth in claim 1, wherein said deflecting channel is situated in the throat plate, said deflecting channel having a deflecting edge for the thread chain, whereby said deflecting edge extends angularly of the path of motion of the work pieces and away from this path.

3. In a sewing machine as set forth in claim 1, wherein said presser foot has a leading groove lyingin the section of said deflecting channel for said thread chain, said leading groove likewise extending angularly of the path of motion of the work piece and away from this path.

4. In a sewing machine as set forth in claim 1, wherein said thread chain feeding dog has a row of teeth and acts together with a guiding surface for the thread chain, said guiding surface and said thread chain feeding dog being arranged beyond the throat plate.

5. In a sewing machine as set forth in claim 4, a knife clip carrying the counter knife, said knife clip being provided with a deflector, for the trimmed ends of the thread chain, said guiding surface being disposed on said knife c 1p.

6. In a sewing machine as set forth in claim 5, wherein a slippage member is provided for the evacuation of trimmed ends of the thread chain out of the machine, said slippage member terminating in a waste channel mounted at a right angle to the sewing machine.

References Cited UNITED STATES PATENTS 1,765,342 6/1930 Lutz 112-252 1,855,301 4/1932 Lutz 112 252 2,592,463 4/1952 Phillips 112252 X 3,143,987 8/1964 Daniel et al. 112252 3,149,594 9/1964 Buckreus et al 112-252 3,181,490 5/1965 Kawasaki ll2252 HERBERT F. ROSS, Primary Examiner. 

